Jump Quest IV

Review — the arc so far 5 min

• Gravity changes the speed; the speed changes y; a jump sets the speed.
• land pushes out of floors and ceilings; walk undoes moves into walls.
• A hitbox costume does the touching, and nobody ever sees it.

Quick-fire

You can climb your level from bottom to top. Why is it not a game yet?

Today’s Topic 3 min

• A second rule colour: water
• A state variable with play, won and over — from Storm Flight
• A respawn point that a checkpoint can move
• An enemy you can defeat from above

Learning outcome

By the end of this lesson you will be able to:

1. Give a level a hazard, lives and a goal.
2. Move the place a player comes back to.
3. Tell a stomp from a collision using the speed.

Learnt — losing and winning 28 min

1 · A second rule colour

The pit is painted one flat blue, and blue means water. It is the same question as the ground, about a different colour — and a different answer:

if <touching color [#2F80ED]?> then
  change [lives v] by (-1)
  go to x: (-215) y: (-104)
  set [y velocity v] to (0)
end
            

2 · A goal, and a state

Touching the star wins. But the loop is still reading the arrow keys, still falling, still checking the water — so the win needs to stop the game. That is Storm Flight’s state variable:

forever
  if <(state) = [play]> then
    land :: custom
    if <touching (Star v)?> then
      set [state v] to [won]
      switch costume to (pico happy v)
      say [Level complete!]
    end
  end
end
            

Basic — the level 24 min

Open your climber from last lesson. Today it becomes a game you can win and lose.

Step 1 — two new variables

1. Make lives and state, both with their monitors showing.
2. When the flag is clicked, set lives to 3 and state to play.

Step 2 — the water bites

1. Delete last lesson’s if <(y position) < (-150)> then check — the water does that job now.
2. After land, add the water check from Learnt part 1. Pick the blue with the eyedropper.
3. Inside it, if lives has reached 0, set state to over and say so.

Step 3 — the whole game inside one if

1. Put an if <(state) = [play]> then inside the forever.
2. Drag everything that was in the forever into it.
3. Change the star check so it sets state to won.

Step 4 — play it both ways

1. Win it. Check nothing moves afterwards.
2. Then lose on purpose three times, and check the game really ends.

when flag clicked
set rotation style [left-right v]
go to x: (-215) y: (-104)
set [y velocity v] to (0)
set [lives v] to (3)
set [state v] to [play]
forever
  if <(state) = [play]> then
    if <key (right arrow v) pressed?> then
      point in direction (90)
      walk (4) :: custom
    end
    if <key (left arrow v) pressed?> then
      point in direction (-90)
      walk (-4) :: custom
    end
    change [y velocity v] by (-1)
    change y by (y velocity)
    land :: custom
    if <<key (space v) pressed?> and <(on ground) = (1)>> then
      set [y velocity v] to (12)
    end
    if <touching color [#2F80ED]?> then
      change [lives v] by (-1)
      go to x: (-215) y: (-104)
      set [y velocity v] to (0)
      if <(lives) = (0)> then
        set [state v] to [over]
        say [Out of lives.]
      end
    end
    if <touching (Star v)?> then
      set [state v] to [won]
      switch costume to (pico happy v)
      say [Level complete!]
    end
  end
end
            

A checkpoint

Put a flag on step 2. Once Pico has touched it, the water sends Pico back to the flag instead of the start.

• Two variables, respawn x and respawn y, set to the start when the flag is clicked.
• The flag changes costume when it is reached, and moves the respawn point to itself.
• The water now uses go to x: (respawn x) y: (respawn y).

A crab on patrol

Add a crab that walks back and forth along the right-hand bank.

• It walks 30 ticks one way and 30 back, for ever — Cheese Maze’s patrol.
• Touching it costs Pico a life and sends it to the respawn point.
• The crab stops when the state is not play.

The stomp

Landing on the crab should defeat it. Walking into it should still hurt.

• Touching the crab while y velocity is below 0 — falling — is a stomp.
• A stomp hides the crab and bounces Pico up a little.
• Any other touch costs a life, as before.

if <touching (Crab v)?> then
  if <(y velocity) < (0)> then
    broadcast [stomped v]
    set [y velocity v] to (8)
  else
    change [lives v] by (-1)
    go to x: (respawn x) y: (respawn y)
    set [y velocity v] to (0)
  end
end
            

Ship it

Put the whole arc together into a platform game you would hand to somebody else.

• A title that explains the keys, then a round that starts from it.
• Falling, jumping, steps, walls, head bumps and a hitbox.
• Three lives, water, a checkpoint and a crab you can stomp.
• A clock, and a best time that survives the round.

Summary 5 min

• A second flat colour can be a second rule: green holds you up, blue takes a life.
• After a teleport, set the speed to 0 — somewhere new means starting still.
• The whole game sits inside if <(state) = [play]> then, so winning or losing simply stops it.
• A checkpoint is a respawn point kept in variables that the level can change.
• Falling onto an enemy is a stomp; the sign of y velocity tells you which.

Hazard

Anything in a level that costs a life to touch.

Respawn point

Where the player comes back after losing a life.

Checkpoint

A place that moves the respawn point once you reach it.

Stomp

Defeating an enemy by landing on it from above.

Hand in

Save your game. You have finished the Jump Quest arc — a character made of a number that gravity changes, on one screen you painted yourself.